Railway traffic controlling apparatus



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. o NS wwwlwm@ QW March 14, 1944. J. ,.-L VAN HcRN l 2,344,333 v RAILWAY ,TRAFFIC CONTROLLING' APPARATUS z-med sept. 25, 1941 f s sheets-sheet 9 INVENTOR damen/ Vfapn. A BY n HIS ATTQRNEY Patented Mar. 14, 1944 UNITED STATES PATENT FFICEv RAILWAY TRAFFIC ooNTRoLLINGV ArrARA'rUs i James J. Van Horn, Pittsburgh-,I Pa.,

The Union Switcha; Signal Company,

assignor to Swissvale, Ipa., a corporation of Pennsylvania Application September 25, 1941, Serial No. 412279 My Y invention relates to railway traic -con- 52 Claims.

trolling apparatus and is directed more particularly to the control of traffic in a single track, two-direction system of signaling wherein centralized traic control or other suitable manual control is used for establishing the traffic direction. A distinguishing feature of my system is that normally, no code is supplied toy the single track stretch, the only current inthev track being that due to the steady energy which I employ for maintaining the established trafc direction and for other purposes. My system dispenses with all control line wires with the exception of the coded C. T. C. line circuit, if C. T. C.' control is used, as will normally be the case, and with the l.

exception of highway crossing control wherein I employ a line circuit to by-pass the steady energy and code around the highway crossing sections.

One object of my invention is to provide a non-line-wire system of the above type which will be normally deenergized except for the steady energy which is used in the track circuits for block detection. Another object of my invention is to establish the desired traffic direction when proper to do so merely by moving a traffic lever at a control ofce to a position corresponding with' this direction, the checking and safety features of the system being brought into play automatically as a result of such movement. A further object of my invention is to provide` certain inter-,

controls on the C. T. C. machine at thecontrol` office to prevent interference with the established traic direction when the entrance signal-is at proceed or the section is occupied by a train. A

still further object of my invention is to provide f a stick circuit for` the traffic direction control relay at each end of the stretch, which is independent of the code equipment at the control cnice, whereby a traffic reversal cannot be accomplished from the control cnice unless the conditions in the'trackway are proper for such reversal. A still further object of my invention is to provide for the propery control ofhighway crossing signals and electric switch locks in, a system of the character disclosed herein. A further object of myinv'ention is to provide a continuous block indication for the single track stretch. y Other objects, purposes, and characteristic features of my invention will be apparent from the description which follows:

I accomplish the foregoing `objects by: normalto provide traffic locking whereby the absence of steady energy prevents a reversal of the traffic direction; removing thek latter steady energyv and transmitting codedy current over the stretch from the new exit end to the new entrance end to provide block control for the'entrance signal; reapplying steady energy behind the train to reset thegtrack circuits to their normal condition; reclearing the entrance signal to' discontinue the steady energy so as to permit a following move; detecting the exit of a 'train Iby 'means 'of the steady energy received at the exit end following a train movement before a traiilc reversal can be made; employing aback contact of the steady energy detecting relay (FSA) the stick circuit for the traic direction control relay (FSR) so that the latter relay is independent ofthe control ofce and cannot be operated therefrom if steady energy is absent from the track stretch; employing only one pair of control line wires to 'provide a simple but effective highway crossing application of the apparatus embodying my invention; employing frequency code of different code rates for providing a continuous block indication where the stretch includes one or more vpairs of intermediate signals; employing back contact coding for effectively relayingthe steady energy and code at cut sections; and providing a simple yet effective form of electric switch lock control without line wires.

The present invention is an improvement on the inventions disclosed in my copending United States application, Serial No. 410,504, filed on September 1-2, 1941, and the copending United States application, Serial No. 411,481, filed on September 19, 1941, by Crawford E. Staples, both for Railway traffic controllingapparatus.

I shall describe several forms of apparatus embodying my invention, and shall then point out the novel features thereon in claims.

In the accompanying drawings, Figs. 1a, 1b, lc, and v1d taken together., with Fig. la at the left, are a diagrammatic view showing one embodiment V of my invention as applied to, a stretch of single track railway extending between the passing sidings PSl and PS2 at the two ends o f-"the stretch; Fig. la being the control cnice for'this stretch. Figs. 1e and 1f are diagrammatic views showing modified forms of the office equipment shown in Fig. la also Yembodying my invention. Fig. llig' 'is a diagrammatic view embodying my invention, showing a modification of a portion of the apparatus of Fig. 1c in which a polar directional fstick relay replaces the two neutral directional stick relays of Fig. 1'c. Figs'. Zia, 2b, and 2c, @are diagrammatic views" showing' modified my invention. Fig. 4 is a diagrammatic View showing theadaptation of the apparatus for a highway crossing location, also embodying my invention. Fig. 5 is a diagrammatic view embodying my invention and showing a modification of al portion of the apparatus of Fig. 1c in Which back contact coding apparatus replaces the front contact coding apparatus at the cut section of Fig. 1c.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Figs. Ia-Id, inclusive, the stretch of track between the passing sidings PSIY and PS2 is divided by means of the usual insulated rail joints at locations D, E, F, and G into a number of track circuit sections. Each of these track sections is identified by the reference character T with a distinguishing prex which also identiiies the apparatus associated with that section. The signals which govern traiiic movements through the single track stretch are the headblock signals 6 and I0 at the respective ends of the stretch and the intermediate signal 1 at location E. The cutsection location F could likewise be provided with a signal, if desired, by adding apparatus similar to that shown at the intermediate signal location E.

Each section of the single track stretch is,

in reality, provided with two track circuits, one eastbound and one Westbound, each of which includes a code following track relay TR at one end and a source of track circuit energy, conveniently shown as a battery, at the other end. The track circuits could obviously be of the alternating current type and my invention contemplatesv such track circuits, the direct current type being shown only for purposes of simplicity. 'I'he track circuit current is properly coded under the influence of trailic conditions, or as initiated by the operator at the central control oiiice shown diagrammatically in Fig. la. Depending upon the direction of traffic movement, only one orthe other track circuit is effective at any one time as will become clear hereinafter. The control relays involved in an eastbound move generally carry the prefix E or R (for right-hand) and those which control westbound moves include the prefix W or L (for left-hand) in order to make the disclosure more easy to follow.

For simplicity, I make use of but two codes, -these comprising direct current periodically interrupted at the rate of '75 times per minute for approach and 180 times per minute for clear signal indications. The coding is accomplished by means of suitable code transmitters 15CT and IBUCT which are well known. It is understood that for cab signaling purposes, alternating current coded over the contacts of these code transmitters could be superimposed on the direct current track circuits, but this added complication is unnecessary for an understanding of my invention. Following moves are provided for by means of directional stick relays and once traiiic is established in a given direction, no further clearing of the entrance signal is required for permitting entry of a following train.

The relays BWFSR and SEFSR adjacent the two ends of the stretch are manually controlled traiiic direction selecting relays which govern the direction of trafc movement through the the stretch. The communication system by means of which the operator at the C. T. C. machine in the control oiiice (Fig. la) may govern these relays may be of any suitable type, but preferably it is of the selective or code type in which communication is established intermittently by means of impulse codes transmitted over a single pair of line wiresy to the desired control location `or field station. The details of such a communication system do not enter actively into the present invention and it is deemed suflicient for an understanding of the present invention to point out that the trailic direction from right to left or westbound is established by moving the traiicY lever 8 (Fig. 1a) to the left-hand o r L position so as to transmit a suitable code for energizing the traffic direction control relay BWFSR in the field station apparatus at the left-.hand end of the stretch. It is understood that the communication system may also be used to govern the traffic leaving the single track stretch at either end by controlling the signals at such ends, and will also be used to provide an indication of traiiicand apparatus conditions within the stretch, as well as to prevent interference with or reversal lof the established traic direction except under proper conditions, as will be pointed out hereinafter. One form of Comunication system suitable for use in my system is that shown in Letters Patent of the United States No. 2,229,249, grantedto Lloyd V. Lewis on January 21, 1941, for Remote controlsystem, and the general designation of the relays comprising the C. T. C. portion of my system, and the numbering of the terminal wires whichare used to perform analogous functions, corresponds with that used in this patent. n

I shall first describe the general features of operation of the apparatus embodying my invention and shall then described the operation more in detail. VIt will be assumed, for simplicity, that the stretchdoes not include an intermediate signal and that the last traflic movement was westbound so that lever 8 occupies its L position, causing the Westbound traiiic relay BWFSR to remain energized and the eastbound traiiic relay SEFSR to be deenergized. With the Westbound entrance signal I 0L at stop, as shown, steady or uncoded energy ows from the east end (entrance end location G) over the intervening track sections to the West end (exit end. location D) where it is used for the control of the unoccupied block indication light, shown in Fig. la. I shall assume that it is desired to permit a westbound train to enter the stretch. When this indication is received at the control oiiice, a control code may be transmitted to pick up a home stick relay (IULHSR) so as to initiate the operation of clearing'the entrance signal IOL. When this control code is received and relay IULHSR picks up, the steady energy is reaction on the part of the'opera'tor other than 75 remaining track circuits of the stretch, in succession. Removal ofgthe steady energy is detected at the exit end and this permits code to be cascaded from the exit end D to the entrance end G to provide the block control for the intermediate' and entrance signals, whereupon the entrance signal will be cleared'. and the. westbound train may enter. As the train passes signal IBL, the block light at' the control ofilce will light up, to indicate the. occupied. condition. The coded energy will continue tozbe fed to the single track stretch after the train accepts the signalV and enters the stretch, until after the stretch is vacated. It is understood, of course, that the coded energy will be cut olf in the,y rear of the train in order to provide the usual follown ing protection. When the train clears the stretch, coded energy Will again be cascaded to the entrance end and will cause deenergization of the stick relay used for following moves, whereupon steady energy will again be applied at the entrance end unless in the meantime a C. T. C. code has been transmitted to reclear the entrance signal.

In order to reverse the traiii'c direction from westbound to eastbound, steady energy must first be detected at the west end (location D) of the block which permits deenergization of relay BWFSR and energization of relay BEFSR following a reversal of lever 8 to the R position and the transmission of the necessary C, T. C. codes for this purpose. When the eastbound traffic direction is established, steady energy will again be present in the track sections of the stretch, as for the westbound traflic direction but this steady energy will now be transmitted in the direction from west to east. Transmission of a C. T. C. code to clear the eastbound headblock signal 6R will. remove the steady energy and so will initiate the supply of coded energy from the east end (location Gf) to the new entrance end Y (location D) in the manner described above for permitting signal 6R to clear so that eastbound traffic may enter the stretch.

Having described the general features of operation, I shall next describe more in detail the L sequence of operations occuring when traine is established in a given direction, assumed to be westbound for purposes of explanation. The basic operation can be most easily understood by first connecting Figs. la and lb directly with l Fig. ld to eliminate the complication of the intermediate signal location and the cut section apparatus.

With the entrance signals 6R and IOL which govern moves into the single track stretch at stop, and with trac lever 8 in its L position for a westbound movement, the apparatus will be in the condition shown in the drawings wherein the westbound traiiic direction control, relay BWFSR will be energized and the opposing or eastbound traffic direction control relay SEFSR will be deenergized. At location G, relay I QLTCTM will be steadily energized over a circuit which includes the back point of contact 23 of relay lRWSR the function of which will be explained hereinafter, back contact 2@ of the home stick relay IBLHSR which controls signal IL, back point of contact 25 of the eastbound traino direction control relay 8 EFSR, back contact 26 of relay ILSR which is the stick relay for signal IBL and picks up when the train passes this signal at any proceed indication, front contact 2l of the track repeater relay STM which is picked up when the short entrance section 9T is unoccupied, and front contact 26 of relay lilLKlVi which checks the stop position of signal IDL and is picked up when this signal is at stop. Steady energy from the direct current source ES is thus applied across the rails at the westbound entrance end over the front point of contact 29 and front contact 3U. of relay IIILTCTM which now remains constantly picked up. Accordingly, relay BRTR at the exit: end is maintained steadily energized over the back point of contact 3l. of relay BRTCTM which is deenergized at this time. Relays GRTM and 6RTFSA will be continuously energized over the front contacts 32 and 334 of relays SRTR and RTM, respectively. The circuit for relay IiRTCTM will, of course, be open at the back contact 34 of relay BRTFSA. The presence of steady energy at the westbound exit end D provides the unoccupied block indication (Fig. la) and makes it possible for the operator to transmit a control code to clear the entrance signal EULA or IIlLC.

When the operator transmits this signal-clearn ing code, he will energize the signal control relay ILHSR (Fig. ld) through the code equipment at. the eld station (231) and will thusr interrupt the steady energy circuit previously traced for relay IQLTCTM at back contact 24 of relay IIELHSR. The signal cannot, however, be cleared until code from the exit end is transmitted over the track and is received at the entrance end, as will appear more clearly hereinafter. Steady energy will now be removed at the entrance end. Absence of steady energy at the exit end will result in the release of relays BRTR, ERTM, and GRTSFA at that end, Whereupon a coding circuit for relay BRTCTM will be completed over the back Vcontact 34 of relay BRTFSA, now closed. vRelay SRTCTM will follow either 75 or 180 code, depending on whether the home relay @LAI-IR for signal GL is deenergized or energized, respectively. As shown in the drawings, this relay is deenergized so that the '75 code circuit for relay ERTCTM will include the back point of contact 35 of relay GLAl-IR, back contactA 3d of relay GRTFSA (now closed), front point of contact 36 of relay SWFSR, back contact 31 of relay ERSR, front contact 38v of relay 5TM, and front contact 39 of relay GRKM. Relay IiRTCTlVI follows the '75 code and applies this code to the exit end D over the front points of its contacts 3l and M).

Looking again at the entrance location G, relay IIlLTCTM at this location is deenergized so that the code following track relay iLTR is con tinuously connected across the rails over the back point of contact 29 of that relay and so will follow the code supplied at the other end of the stretch. Relay. IDLTM which is controlled over the front point of contact 4I of relay IIJLTR and is of the code following type will likewise follow the code and will cause the energization of the front contact repeater relay IULTFSA over its front Contact 42. The back contact repeater relay IBLTBSA will likewise be energized over the back point of contact 4I of relay IEJLTR and the front contact 43 of relay IDLTFSA. Relay IBLTBSA serves as an approach energizing relay for the decoding circuit of the decoding transformer DT which now becomes energized over the front contact fili of relay ILTBSA and the coding contact 45 of relay IULTM. Code detecting relay ILCDR will now become energized from the output of the decoding transformer over the rectifying contact 4% oirelayr IilLTM, in the usual manner. Since relay IBLCDR is energized, the circuit for clearing signal ISLA or'IOLC may be completed in the usual and well-known manner.

When the train passes signal IDL, relay SQLHSR (Fig. 1d) will become deenergized due to opening of frontcontact 4l ofrelay STM in its stick circuit so that if no additional lever manipulation involving this stretch is made, '75 code will be applied to section GRT as soon as the train vacates this section, in order to permit following moves to be made. Relay IGLTR will again respond to this code and will .energize relay IULCDR, as before, thus deenergizing the directional stick relay IDLSR. at back contact 50 of relay IULCDR. The westbound stick relay IULSR will have been picked up over the back contact A8 of relay STR and the front point of contact 49 of relay IDLAHR. The stick circuit for relay -lllLSR. includes back contact 58 of relay |LCDR, back points of contacts 5| and 49 of relays ||lLCHAR and IULAHR, and front contact 52 of relay lLSR. The release of relay IBLSR completes the pick-up circuit for relay IULTCTM at back contact 26 whereupon this relay now becomes steadily energized over the circuit previously traced. The continuous energization of relay iLTCTM causes steady energy to be applied to the westbound entrance end G, whereupon relay SRTR will become energized during oil intervals of the code which is being supplied at the westbound exit end D. That is to Say, the steady energy will feed through during the oir" intervals in the code. Energization of relay GRTR causes energization of relays GRTM and GRTFSA, as before, whereupon relay GRTCTM will become deenergized due to the opening of back contact 34 of relay SRTFSA, and will re- -main in this condition until signal IBL is recleared or until a traiic reversal is initiated.

summarizing the operation described thus far, the receipt of steady energy at the exit end permits initiation of the clearing operation for the entrance signal in which the steady energy is cut off at the entrance end and when this effect reaches the exit end, coded energy is ap plied at that end and is detected at the entrance end. Presence of code at the entrance end permits completion of the clearing operation for the entrance signal.

A train entering the stretch provides for following moves by picking up a directional stick relay. When the train vacates the stretch, code is reapplied at the exit end, releasing the directional stick relay which reapplies steady energy at the entrance end. This steady energy feeds through the code and when detected at the exit end, cuts oi the code at that end so that the apparatus is restored to its normalV condition.

I shall now describe the manner in which a reversal of traflic direction from westbound to eastbound is accomplished, stillassuming that no intermediate signals are present so that Figs. la, 1b, and 1d;y only are used.

With relay GRTR steadily energized due to the presence of westbound steady energy in the stretch, relay GR'IFSA will be energized and code detecting relays GRCDR and BRDR will. be deenergized. Since the last traino movement was westbound, the trafiic direction relay BWFSR will be energized so that a circuit will be completed for energizing terminal 90 of the eld station unit (234) (Fig. 1h). This circuit includes the back points of contacts 16 and 'I'l of relay BRDR and SRCDR, respectively, and the front points of contacts 18 and 19 of relays BRTFSA and BWFSR, respectively. Energization of terminal 90 of the eld station unit results in the transmission of a C. T. C. code to the control oflice in a manner which will be clear from the Lewis patent. This code will cause the westbound block indicator relay 8WTK to become energized. With this relay energized, the direction of trailic may be reversed by a movement of the traiic lever 8 to its right-hand position in which contact 8E is closed and contact 8W is opened. When this lever movement is made, a circuit is completed to one winding of the polarized relay BLPR over the front contact |09 which closes during the initial movement of the lever, front contact |08 of relay SWTK and the lever contact 8E of lever 8. When polar contact I|0 of relay SLPR moves to its left-hand position corresponding to this energization, a control code will be transmitted to the field station unit (236, Fig. 1d) to energize the eastbound direction control relay BEFSR. The initial movement of lever 8 caused the starting relays 236ST and ZMST to become energized so that corresponding codes were transmitted to the eld station units, as is well known in C. T. C. practice as exemplied in the Lewis patent. The code resulting from energization of the starting relay 236ST caused the pick-up of the eastbound direction control relay 8EFSR, as just described. The vcode transmitted by virtue of the energization of the starting relay 234ST caused the release of the westbound direction control relay BWFSR. Relay 8WFSR will release due to the interruption of the circuit to terminal |02 which extends through contact |75 of relay 234s, at the polar contact I0 of relay 8LPR, now reversed so that contact |||l occupies its lefthand position.

It will be observed that if relay SEFSR. becomes energized beforerelay BWFSR is released (which may happen due to the fact that codes must necessarily be transmitted to the different eld station units in succession) the energization of relay BEFSR will cause relay IQLTCTM t0 respond to code instead of steady energy. Accordingly,l coded energy will be applied instead of steady energy at the new entrance end (location G) and the code will be detected by relays GRTR, ERTM, BRTFSA, and BRTBSA, at location D. Since relay BRTFSA is thus continued in its energized position, no change in the traic set-up at location D will occur until relay SWFSR is subsequently deenergized. When Vthis occurs, relay SRTCTM will be continuously energized over the circuit which includes the back point of contact 2li! of relay 1RWSR, back contact 55 of relay SRHSR, back contacts 36 and 31 of relays BWFSR and BRSR, respectively, and front contacts 38 and 39 of relays 5TM and BRKM, respectively. Since relay BRTCTM is now steadily energized, it disconnects relay GRTR from the track at the back point of its contact 3| and thereby releases relays BRTM, SRTFSA and SRTBSA. Steady energy will now be applied at the new entrance end (location D) for the eastbound trafc direction over the front point of contact 3| of relay GRTCTM so as to energize relay IDLTR at the new exit end (location Gr). At the same time, coded energy is being applied at this new exit end.

` IBLTFSA, in sequence. The energization of relay IULTFSA will deenergize relay IQLTCTM at its back contact 56 so that coded energy will be removed from the east end (G) of the stretch. y

Steady energy will continue to be supplied at the Westend (D) until signal 6R is cleared for the eastbound move, whereupon steady energy will be removed because of the energzation of rel-ay SRHSR which has a back contact 55 ilcluded in the steady energy supply circuit vfor relay GRTCTM.

If relay WFSR becomes deenergized beforerelay 8EFSR picks up, then relay GRTCTM ywill be energized on steady energy and will impress steady energy on the track at location D. This steady energy will oppose the steady energy impressed on the track by relay IULTCTM at location G, but this will have no adverse eiect. As

soon as relay SEFSR picks up, relay IULTCTM will have its energization changed from steady to coded, thus permitting relay lLTR to become energized on the first ofi interval of the code, with the consequent energiaztion of relays vl OLTM and IULTFSA. Pick-up of relay IiL'IFSA will `denergize relay lliL'ICTM and so will discontinue the supply of coded energy to the track. The track will now have steady energy alone iiowing in the rails from the new-entrance end D to the new exit end G. From this point on, the establishment of the eastbound traiiic direction will be clear from the analogous description already presented for the westbound traic direction.

Having described the basic operation employing Figs. la, 1b and 1d, I shall now vdescribe the operation taking vplace when the single track stretch includes an intermediate signal location and a cut section location. For this purpose, Fig.

1c is inserted betweens Figs. 1b and 1d or" the drawings. To avoid unnecessary duplication, the present description will be conned as much as possible to the apparatus of Fig. 1c.

With trac assumed to be established lin the westbound direction, as before, and the stretch unoccupied, steady energy is fedgin the direction of tra-flic from location G to location D. When this steady energy is received at location F, relay TAETR will be energized over .the back point of contact 5T o relay TAECTM and will energize relay TAWCTM over its front contact 58. Relay TAWCTM will apply steady energy from the track battery IS to section TRT over the front pointer its contact 59 and front contact |16. At the intermediate signal location E, the steady energy will energize relay TETR as `well as relays TETFSA and TWCTM.' All other relays at `this location (except the codetransmitters) will be deenergized. The circuit for relay TWCTM includes the iront point ,of contact -60 of relay TETFSA, the back points Lof contacts 6l and 62 of relays TES and THR, respectively, and the back contacts 63 of relay TWS. `Steady energyis repeated into the section BRT. overtheffrontpoint.

of contact ITT and the front contact 64 lor" relay TWCTM. Accordingly, the vmanner in which steady energy can be readily-.transmitted around a out section location as well as an intermediate signal location in the system embodying my invention will be readily apparent. j

I shall next describe how a control is established for clearing the entrace signal IDL for :a westbound move. Energization of the stick relay IOLHSR to clear one of the lilla signals removes*` the steady energy from the westbound entrance c end at location G and causes the `deenergization of relays TETR, TETFSA and TWCTM at the intermediate signal location E. Steady energy will consequently be removed from section` BRT so that relay ERTR will also release. The absence of steady energy at location D will-cause coded energy to be applied to section GRT, due to the releaseof relay SRTFSA, as explained hereinbefore. This Coded energy will be detected by they `code following Operation of .relay TWTR and by the energization of relays TWTFSA, TTM, TESA, THR and TWS, if the code is 75. Relay TWTFSA will remain steadily picked up, as will relays TBSA, THR, and TWS. Relay TTM iS ,a 69de iollowing relay which is now energized over the back point of coding contact ITlof relay TWTR and the front point of contact ITS of relay TWTFSA. The code operation of relay TTM will accordingly energize the code detecting relay THR over the rectifying contact it. The circuit for relay TWS includes frontcontact 'Til of relay THR, back point of contact TI of relay TE'IFSA, and the front point of contact T2 of relay TWTFSA. If the code supplied .to section BRT is 180, the 180 code detecting relay TDR will also be energized so that signal 1W will then display either an approach or a clear indication, depending on the code.

Relay TECTM will now follow 180 code and will apply energy of this code Afrequency to the section TRT and when the 180 code is detected at location Gsignal lL will be permitted to display a clear indication. The circuit for relay TECTM under this condition will include the .back point of Contact 60 of relay TETFSA, wires65 and-66, contact ET o f coder ISUCT, front point of Contact 68 of relay THR, and back contact -69 of the opposing directional stickrelay TES. Now, when the train passes signal TW, shunting out relay TWRT, all of the relays TWTFYSA, TTM, TBSA, THR and TDR will become deenergized. The

westbound directional stick relay TWS is slow in Areleasing and so will establish an obvious stick circuit for itself `over the back point of contact T3 of'relay TWTFSA and its own front contact T4. Relay TECTM will now follow code, its coding circuit including the backpoint of contact 60 of relay TETFSA, wire ISI, code contact 15 of the coder 15CT, Viront point oi contact T6 of relay TWS, back point of contact 68 of relay THR, and back contact 69 of relay TES. Accordingly, 75 code is applied by relay TECTM to the section TRT, although this code is as yet ineffective in this section due to occupancy by the train.

When the train vacates section TRT, the 75 code will cause operation of relay IfLTR at 1ocation G so that the .code detecting relay IOLCDR will be energized. Energization of this relay will open the circuit of the'stickrelay IDLVSR (which lbecame energized when the ltrain passed signal IBL) toprovide a control for-permitting a followvingmove to -be `made into the occupied stretch. Deenergization of relay IULSR will permit the th-rough the codeto location E and will be detected during the oir' intervalsof the code by relays TETR and TETFSAatthe intermediate signal location. vThe energization of relay .TETFSA opens the coding circuit for relay TESTM which --was-just traced,at the back point of contact 60,

thus removingcoded energy from section TRT.

It will be notedthat the steady energy which is `applied at location -G cannot be relayed to the other end D of the stretch until coded energy Vhas v been received Afrornsuch other `end to deenergize `7o,

[relay vi'worivr.` The deenergizauon ofrreiay 1Ws the westbound directional stick relay TWS which has a back contactA S3 inthe energizing circuit for will take-place when thei train clears the sections BRT and 5T between signals TW and 6R, Where- "7,5,

upon coded track energy `will'be -applied'at location D and will result in the energization of relays "IWTR and TWTFSA, thus interrupting the stick circuit for relay 'IWS at the back point of contact i3 of relay '|WTFSA. When relay 'IWS closes its back contact 63, relay TWCTM will become steadily energized over a circuit which includes the front point of contact 60 of relay 7ETFSA, back points of contacts 6| and 62 of relays 'IES and 'II-IR, respectively, and the back contact 63 of relay 'IWS.

During the time that a westbound train is between the signals 1W and 6R, a following move may be made by reenergizing relay IULHSR at location G through the C. T. C. system, thus removing the steady energy from the track sections between signals 'IE and IOR. Now, with relay 'IWS energized, relay 'IECTM will follow 75 code and will apply this code to sections 'IRT and |0LT. The energizing circuit for relay 'lECTM will be the Vsame as previously traced in connection with the passage of a westbound train beyond signal 1W. The detection of the 75 code at location G will permit one of the |L signals to display an approach indication for the following train, as will be obvious.

I shall next describe the operations involved in a reversal of trac when the stretch includes an intermediate signal location. In connection with this reversal of the traffic direction from westbound to eastbound, reference will be had to the apparatus at the `control cnice or C. T. C. machine shown in Fig. la. To accomplish theireversal of the traic direction to eastbound, steady energy must be flowing in the westbound direction from location G to location D in order that the front point `of contact 18 of relay GRTFSA in the energizing circuit for terminal 90 of the eld station unit of Fig. 1b may be closed so that this terminal will be energized under the assumed condition. Accordingly, a code will be sent out vfrom this field station to the control office of Fig.

la so that relay 8WTK on the C. T. C. machine will be energized in order to permit a reversal of the polarized relay 8 LPR which is controlled by the traic lever 8. As previously pointed out, the steady energy will follow a train as it passes over the stretch, progressively energizing the track -circuits and associated apparatus until when the train completelyY vacates the stretch, all of the track circuits will be reset on steady energy which is the normal condition oi the system. The energizing circuit for terminal 90 of the iield station unit also includes the back points of contacts 16 and-11 of code detecting relays SRDR and BRCDR (both deenergized since code is absent from section SRT) andthe front point of contact 19 of the westbound traino direction control relay SWFSR, in addition to the front point of contact 18 of relay SRTFSIA, mentioned above. Relay SWFSR is still energized since the last traiiic movement was westbound. Y

The preliminary movement of the traine lever 8 results in the pick-up of both starting relays 234ST and 236ST which control the transmission of C. T. C. codes to the iield stations 234 and 236 at locations D and G, respectively. Thecode transmission circuit for energizing the respective traiic direction control relay for the new directionY will, however, not be completed until a reversal of the polar stick relay SLPR which remains in its last energized position, is obtained. Under the condition assumed, relay 8LPR will receive reverse energization over the lever contact 8E (now closed), front contact |08 of relay 8WTK, and lever contact |09 (lever contact |09 75 having become closed during the preliminary movement of the lever 8). At this point it is advantageous to call attention to the traflic locking functions performed by the apparatus embodying my invention, with .special reference to the apparatus of Fig. 1a. As will now be apparent, the westbound block indication relay 8WTK (or terminal of the eld station unit) cannot be energized unless the stretch is unoccupied and the westbound signal |0L is at stop so that westbound steady energy flows over the stretch. The energization of relay 8WTK closes front contact |82, and since polar contact ||0 of relay 8LPR is in its right-hand position, the Westbound traic relay SWFK is energized over an obvious circuit, closing a circuit over its front contact |20 for the westbound traiiic direction light 8WFKE. If now a C. T. C. code is transmitted by the operator to location G for initiating the clearing of signal |0L, the steady energy will be removed from the stretch for reasons hereinbefore pointed out. The same will be true if the stretch is occupied, or the westbound steady energy is removed for any other reason. As a consequence, relay GRTFSA will release, deenergizing terminal 90 and causing relay 8WTK to release. longer possible to reverse relay 8LPR even if the traffic lever itself is reversed to close contact 8E, because the reverse energization for relay 8LPR is interrupted at front contact |08 of relay 8WTK. It will be clear, therefore, that polar contact ||0 is now locked in the right-hand position corresponding with westbound trairc so that no traic reversal can be-accomplished unless westbound steady energy is restored over the stretch. The westbound traino relay WFK will, in the meantime have its stick circuit closed over polar contact ||0 to the right, wire |83, and its own front contact |84 so as to maintain the westbound trailc direction indication during the time that signal |0L is clear or the stretch is occupied by a westbound train. It will be apparent, therefore, that the apparatus embodying my invention provides a highly effective, yet relatively simple form of traflic locking which prevents interference with authorized movement of trafc or the reversal of traffic direction when such reversal cannot be properly and safely accomplished.

Continuing now with the previous description in which a reversal of relay BLPR has been obtained, contact ||0 of relay 8LPR is now closed in the reverse or left-hand position and since relay 236S is now energized, energy is supplied to terminal |04 of the oiiice unit which terminal corresponds with the similarly numbered terminal of the Lewis patent. The circuit for terminal |04 includes polar contact 0 in its left-hand position, wire |85, and front contact |86 of relay 236s, now closed. Energization of terminal |04 results in the transmission of a code which causes pick-up of the eastbound traic direction control relay 8EFSR at the eld station 236 at location G. When relay BEFSR picks up following the movement of lever 8 to its R position, the steady energy previously supplied at location G over the back point of its contact 25 willV be discontinued and will be replaced by code* supplied over the front point of contact 25, as-before. When relay 8WFSR at the other end becomes deenergized, steady energy will be supplied at location D, 'as previously explained. i y Referring again to the intermediate signal location E, the foregoing reversal of Vlever'to its eastbound position will produce the 'following circuit operations. The steady energy which was Accordingly, it is now nopreviously applied at location G when the traflic direction was westbound caused relays 1ETR, 'FETFSA and 'lWC'IM to be steadily energized. When the change to code supplied at location G occurs, relays l'IM, 1138A, IHR, and 'IES will also become energized. Relay lWCTM will now operate on code, its circuit including the back point of contact 'i3 of relay 1WTFSA, wire lll, contact Il2 of code transmitter IBDCT, front point of contact 62 of relay lHR, and the back contact 63 of relay WS. The code operation of relay lWCTM will cause code to be supplied to section ERT beyond the intermediate signal 1W.

Considering now the other end of the stretch at location D where steady energy is now being applied because of the release of relay WFSR, the application of this steady energy will also be detected at the intermediate 'signal location E by the steady energization vof relays EWTR and 1WTFSA since the steadyv energy will feed through the code during the off intervals, as previously pointed out. Pick-up of the 'latter relay opens the circuit ror relay 1WCTM, thus removing code from section SRT. The pick-up of relay IWTFSA also opens the circuits of relays IES, 1'I'M, IBSA, and II-IR, whereupon relay lECTM will become steadily energized and will relay the steady energy from section SRT into sections IRT and lLT. The steady energy circuit for relay lECTM includes the front point of contact 'i3 of relay lWTFSA, back points of contacts 16 and $8 of relays 'HWS and THR, respectively, and back contact E9 of relay IES. The steady energization of relay lECTM results in the obvious deenergization of relays lETR. and 1ETFSA. Ac-

cordingly, the stretch has now been reset on eastbound steady energy so that the operator may initiate clearing of the eastbound signal 6R to permit an eastbound train to enter the stretch.

The operation of the rapparatus at the intermediate signal location when an eastbound train moves over the stretch is similar to the previously described operation for a westbound train movement, so that this description need not be repeated. Also, the operation of the apparatus at the cut section location will be clear from the previous description without added explanation.

I shall next describe the block indication features of my invention, considering first that the stretch has no intermediatesignals, as will be the case When Figs. la, 1b, and ld Iare placed end to end. Figs. 1b and 1d of the drawings, when Fig. 1c covering the intermediate signal location is inserted therebetween, show the block indication apparatus for a stretch of track having one intermediate signal and this indication apparatus has already been described. Figs. 2a, and 2by show the modifications required' in the control for the track indication relays SWTK and SETK, respectively, when no intermediate signals are involved as is the case when Fig. 1c is removed from the stretch. Referring to Fig. 2, with steady energy in the track being supplied at location G and feeding westbound, as will be the case for westbound tralic, a circuit for causing energization of the Westbound track indication relay SWTK located at the control oiiice will be completed over the back point of contact l I3 of relay SRCDR and the front points of contacts IM and H5 of relays BRTFSA and 8WFSR, respectively, to terminal gil of the field station unit. As pointed out hereinbeiore, energization of terminal 9i! causes the transmission of a code from the eld station to the control oice to cause energization cf'relay SWTK. 'Relay ETK-(Fig. 2b) re- 75 sponsive to code from the opposite end of the stretch is, of course, deenergized at this time. Accordingly, the circuit for the block light which includes back contacts Ii and ill of relays SWTK and BETK, respectively, is incomplete so that the block light is dark and the indication is unoccupied block.

When code is applied at location D and transmitted over the stretch for a westbound move, a circuit will be effective for energizing terminal 9B of the lleld station unit 236 at location G over the iront point of contact H8 of code detecting relay IELCDR (now energized) to cause the energization of relay BETK at the control office through the transmission of a suitable C. T. C. code. Relay 8WTK will at this time be deenergized because of the deenergization of terminal Siti of the eld station unit 234 resulting from the removal of steady energy from the track. Accordingly, the circuit for the block light will again be incomplete so that the indication is unoccupied block. If a westbound train should now enter the block, relay lDLCDR will be deenergized and so vwill complete a circuit over the back point of its contact H8 and the back point of contact H9 of relay IGLTFSA (now also deenergized) so as to energize terminal all of the field station unit which results in the transmission of a C. T. C. codeto deenergize relay SETK at the oice. With relays SWTK and ETK both released, the circuit for the blocl; light will be completed at back contacts H6 and ll'l so that 'they block light will lnow indicate occupancy of the single track stretch.

Considering next the trailic indication, it is unimportant as to which of the two trac directional control relays (8WFSR or SEFSR) is operated first when the traic direction is changed from westbound to eastbound, as the final circuit condition Will be such that relays GRCDR,

(iRfPlSA, and WFSR will all be deenergized so that a circuit will be completed for energizing terminal E4 of the eld station unit 234i so as to cause denergization of relay BWTK at the oiii'ce. On the other hand, relays lilLTFSA and SEFSR will be energized so that a circuit will be completed for energizing the terminal Qt of the iield station unit 236 so as to energize relay BETK. The time required to complete these relay operations and the order in which the indication codes are transmitted may produce a condition such that the block light may be illuminated for a short interval of time even though the block is then unoccupied. This type of indication will ordinarily not persist for more than a very few seconds unless the indication codes are delayed by control codes which receive preference in transmission.

The reversal of the polar contact iii) of relay SLPR when the traic direction was changed from westbound to eastbound opened the circuit for the westbound traffic relay SWFK whereupon the opening of front contact l2!) of this relay caused the westbound traffic indication light SWKE to become extinguished.

The energization of relay SETK with the polar contact Htl of relay SLPR closed to the left (for eastbound traffic) completes the circuit for the eastbound tramc indication relay tEFK over its front contact 21. The latter relay, in turn, closes its front Contact l22 to illuminate the eastbound trafc direction light SEFKE. Relay SEFK is provided with a stick circuit over its own front contact |23 and Wire |85 so that it will remain 4energized as YVlong as relay SLPR has its contact l closed to the left for the eastbound tramo direction. This provision is expedient since relay 8ETK will become deenergized when a control is transmitted to clear the 6R signals and eastbound steady energy is discontinued.

Where the stretch includes one pair of intermediate signals the block indication will be provided by the apparatus shown in Figs. 1b and ld, as previously pointed out. This apparatus is the same as that shown in Figs. 2a and 2b and described above, with the exception that since one pair of intermediate signals is present within the stretch, the 180 code decoding relays (ERDR and IBLDR) at the two ends of the stretch are used in the circuits for energizing the terminal 90 of the respective field station unit,`to pick up the track indication relay, and in the circuits for energizing terminal 94 which causes a release of this relay. The circuit change occasioned by the addition of relays GRDR and IOLDR will, accordingly, be clear from the drawings without added description. As before, relays 8WTK and BE'IK will detect the unoccupied condition of the stretch when steady energy is present throughout the stretch.

If the stretch includes more than one pair of intermediate signals, line wire circuits may be used as shown in Fig. 2c to repeat portions of the stretch to provide controls equivalent to those shown in Figs. 1b and ld. Fig. 2c shows the use of such line wire circuits for two sets of intermediate signals. In this gure, the contacts |24 and |25 of relays A and B would be substituted for contacts 16 and |26, respectively, of the corresponding relays BRDR and IULDR of Figs. 1b and 1d, respectively. In all other respects, the control circuits for relays BW'IK and ETK will remain as in Figs. lb and 1d.

Referring to Fig. 1g, the apparatus shown in this ligure is similar to that shown in Fig. 1c with the exception that instead of using two neutral directional stick relays WS and ES, one for each direction, I employ a single directional stick relay DS. 'Ihis relay is of the polar stick type and operates its polar contact |10 to the left when energized with current of one polarity over a circuit which includes the back point of contact |1| of relay WTFSA, front contact |12 of relay HR, and the front point of contact |13 of relay ETFSA. When the traic direction is reversed, relay DS will open contact |10 and will close its polar contact |14 to the right by virtue of an energizing circuit which includes the back point of contact |13 of relay ETFSA,; front contact |12 of relay HR, and front point of contact |1| of relay WTFSA. Polar contacts |10 and |14 control the application of code for a westbound or an eastbound following train movement, respectively, in a manner which will be clear from the previous description.

Referring next to Fig. 3a, this figure shows the apparatus embodying my invention applied to the control of an electric switch lock within the single track stretch, the lock being associated with an intermediate signal. The various relays in this ligure carry similar designations to those used for the relays in Figs. lb, lc, and 1d, and these relays preform broadly the same functions so that it will be necessary to describe only those features wherein the apparatus of the present iigure differs from that of Fig. l. It will be understood, of course, that Fig, 3a can be substituted, for example, for Fig. lc, or inserted between Fig. 1c and either Fig 1b or 1d to provide a complete,

operative system for electric switch lock control. The switch lock lever 1 shown in the control oiiice apparatus of Fig. la is provided for the purpose of effecting such control when the apparatus of Fig. 3a forms a part of the single track system.

In the system embodying my invention, a train on the main track may secure an unlock automatically and enter the siding without any additional action being required on the part of the operator at the control office. In this case, the unlock is obtained when the train occupies the short releasing track section OT which may be of the order of 100 or 150 feet in length. The circuit for energizing the switch lock 1BW includes the back contact |21 of the track relay OTR for the section OT and the reverse Contact |28' (now open) of the manually operable lever 1A which the trainman operates fbefore an unlock is obtained. The trainman will reverse both levers 1A and 1B, allowing a train to enter the siding, whereupon .both of these levers should be restored to the normal position, as shown, unless the train is to leave before the arrival of another train. The purpose served by lever 1A will be explained in connection with the operation involved in obtaining an unlock to permit a train to leave the siding. This operation will now be described.

In order to render the switch lock operation more readily understandable, I shall assume that Fig. V3a has :been substituted for Fig. 1c in the system of Fig. 1 and shall first point out briefly the main steps taking place during the operation of obtaining an unlock. 'I'he action of throwing the bolt lock lever 1A cuts off the steady energy (assumed flowing westbound) at the track switch location, resulting in current of '15 code feeding back from the west end to the switch location, and also lighting the block light on the operators control panel. Obviously, unless steady energy is present at the track switch location, throwing the lbolt lock lever 1A `will have no effect.

The illumination of the .block light indicates to the operator that the bolt lock has 4been thrown, and that he may reverse the switch lock lever 1 at the control oflice. This operation transmits a C. T. C. code to location G (the iield station where the steady energy originates) for the purpose of cutting off the steady energy at that location and applying code. When code is received from both directions at the switch location, the electric lock lbecomes energized so that the track switch may now be reversed.

I shall now describe the operation more in detail. As pointed out above, in order to secure an unlock for a train on the siding, the trainman will rst operate lever 1A. It is assumed that traflic has been established in the westbound direction and that steady energy is being fed in the westbound direction from one end of the stretch through the switch lock location to the other end. Traflic should ordinarily be set in the direction of train movement in order to provide intermediate signal control. However, the system will operate satisfactorily with traffic established in either direction. The reversal of lever 1A under the assumed condition results in the deenergization of relay OTWM through the opening of contact |29 of lever 1A (which is closed only in the normal position of lever 1A), as will be obvious from the drawings. Relay OTWM, in releasing, opens the circuit for relay WCTM so that the steady energy is cut 01T from section WT and any other sections west of the intermecause relay ECTM also has its energizing circuitl open at the iront contact |30 of relay OTWM.

The latter relay has been provided with a stick circuit to insure that it will not be deenergized should lever 1A be reversed during atirne .when coded energy is effective in the track circuitsA and an entrance signal is clear, or a trainis approaching the lock. In either case, it would be undesirable to interrupt the coded track circuit energy with the possibility of interfering with the train` movement. The normal pick-up circuit for relay OTWM includes the armature contact |3I of lock 1BW, the normal contacts |32 and |29 of levers 1B and 1A, respectively, front contact |33 of relay O-TR, winding of relay OTWM, front contact |34 of relay OTR, and normal contact |35 of lever 1B. The stick circuit for relay OTWM includes armature contact |3|, normal 1 contact |32 of lever 1B, wires |36 and |31, front contacts |38 and |39 in multiple of relays EHR and WHR, respectively, wire |40, front contact Hl! of relay OTWM, and wire |42. It will be apparent that front contact |4| in this circuit bypasses the normal contact |29 of lever 1A. Contacts 32 and |35 of lever 1B can berthe usual switch circuit controller contacts and need not require a separate lever such as 1B. i l

After the trainman has operated lever 1A under the proper conditions, the operatory at the control oice will send a control code to both ends of the stretch with the switch lever 1 in thc control cnice in its unlocked (R) position. Accordingly, the switch control relay 1RWSR (Fig. 1d) at the entrance end of the block corresponding with the established traliic direction (westbound) will become energized since the eastbound traic direction control relay BEFSR is now deenergized and has its back contact |43 closed. Relay lRWSR at the other end of the block (location l D) will not become energized because the westbound traic direction control relay `8WFSR is energized under the assumed condition of westbound traic and has its back contact |88 open.

The control circuit for relay 1RWSR includes, in addition to the back contact |43 of relay BEFSR, the front contact |44 of relay IDLKM, back contact |45 of relay |0LSR, and back contact |48 of the time element release 1TER. Front contact |44 of relay IDLKM checks that the entrance signals are at stop. Back contact |45 of A the directional stick relay |0LSR prevents the energization of relay 1RWSR if relay IULSR is energized. This provision makes it possible` for coded energy to be receivedafter the train passes the rst intermediate signalto deenergize relay lllLSR, after which steady energy would normally be applied to the track circuit and transmitted in the Westbound direction. Back contact 648 of the time element release 1TER checks that this relay is in its fully released position so that a full time interval will be measured by the relay, when energized. Relays 1TER and1TESR are required only when switch locks are located at automatic signals (as in Fig. 3a), and in this case only at the east end of the block. Thus,

these timing relays are only required at the east end of the block when it is possible for a train leaving a siding equipped with an electric switch lock to pass an intermediate signal and then move past an intermediate signal in the opposite direction. The end of the block toward which such a train movement could be made is the one which would require the timing relays TER and TESR. I

The energization of relay 1RWSR at location-G changes the control circuit of relay IULTCTM from steady energy to code. This control circuit now includes the '75 code terminal, back point of contact |41 of relay |0RAHR,-back contact 58 of relay |0LTFSA, wire |89,` front point of contact 23 of relay 1RWSR, back contact 24 of` relay |0LHSR, back point of contact 35 of relay BEFSR, back contact 26 of relay |0LSR, and front con;-` tacts 21 and 28 of relays vSTM/.and |0LKM. Relay IULTCTM will now applycoded energy Ito the track at location G and this energy will be fed in the westbound direction toward the switch lock location. When this code is detected at the switch lock location by virtue of the energization of relay EHR, the switch lock circuit will become completed over a path which` includes the front point of contact |48 of relay WHR, wire |40, front contact |50 of relay EHR, wires |5I and |52, and reverse contact |28 of lever 1A.

It will be noted that in the case of the intermediate signal type of switch lock location, as shown in Fig. 3a., the circuitl `for the electric switch lock 1BW includes front contacts |53, and |54 of the eastbound and westbound directional stick relays ES and WS, in multiple with front contacts |50 and |48, respectively, of relays EHR and WHR. Accordingly, with this arrangement, an unlock could be obtained at lock 1BW following the movement of a westbound train past the intermediate signal W. i

lAfter the unlock has been obtained and the switch hasbeen reversed, the unlock control may be cancelled by transmitting a C. T. C. code, with lever 1 in the normal position, to deenergize relay IRWSR at location G, thus completinga circuit for the thermal timev element relay` 1'1`ER over the back -contact |55 of relay 1RWSRand the back point of contact |55 of relay 1TESR which became deenergized when relay 1RWSR was energized. After the expiration of the required time interval, the front contact |51 of relay 'ITER will close and will complete anolovious energizing circuit for relay 1TESR. Pick-up of relay 1TESR will open the circuit for relay 1TER at the back point of contact |5B,.thus permitting ythe thermal relay to cool and to reclose its checking contact |46 in thepreviously traced circuit for relay v1RWSR. j Relay 1TESR will remain energized until such time as relay 1RjWSRis reenergized for another unlock of the electric switch lock. l

If the train leaving the siding were to movein the eastbound direction while a westbound train occupied the` block west of the `switch lock, the operator at the control ofce would leave lever 1 in the reverse position so as to feed coded track circuit energy toward the train', as mentioned hereinbefore, in order that the intermediate signals may display proceed aspects. Ii the block were unoccupied, Ithe operator -would have established the eastbound direction of traic `so that the train could proceed east in the usual manner and lever 1 could be restored to its normal position at any time after the switch became unlocked.

In view of the explanation which has been presented above in connection with the apparatus of Fig. `3a for obtaining an unlock of a switch lock at an intermediate signal location, it=is believed that the operation of the apparatus of Fig; 3b will be entirely clear from thev drawings'. This figure shows the switch lock '|BW positioned at a cut section location so that a considerable portion of the apparatus of Fig. 3a can be dispensed with in Fig. 3b. All of the steps involved in the switch lock operation are-the same in both cases, so thata detailed description of the opera-v tion is unnecessary; The chief difference resides, ofcourse, in the absence of the directional stick relays ES and WS; the repeating relays ETM- and WTM; and the decoding apparatus which provides selective control of the intermediate signal indications. Relay OTWM is again provided with a stick circuit` which prevents release of this relay by a reversal of lever 1A at a time when coded energy flows in either direction over the stretch. The code detection in Fig. 3bis accomplished lbly relays ETBSA and WTBSA which will not be energizedfunless the respective track relay ETR or WTR is following code. When code is present, theY stick circuit of relay OTWM will accordingly include one or the other front contacts |90 or |9| of relays ETBSA and WTBSA, respectively, instead of the corresponding contacts |38 or |39 of relays EHR and WHR, respectively, in Fig. 3a.. TheV normal pick-up circuit for relay OTWM is the same in both figures. It is apparent, therefore, that the apparatus lends itself readily to the control of switch locks either at an intermediate signal location or at a out section location. v

In either of the foregoing arrangements, the switch lock lever 1 in the control office may be restored to its normal position at any time after the track switch has been reversed. This is possible because, the track switch does not have to be unlocked inY order to be thrown to normal.

l An unlock of the switch. can also be obtained (following a reversal of lever 1A) if the short detector section OT immediately in advance of the switch isA shunted, releasing relay OTR which closes an auxiliary pick-up circuit for lock 'IBW overk its backv contact |27, wire |52, and reverse contact |28 of lever '|A. This provision makes it possiblel for a train occupying the main single track stretch to` enter a siding at any time.

Referring next to the highway crossing modification shown in Fig. 4, I employ neutral direct current track circuits for the approach control of the highway crossing operating circuits and for the short track circuit through the crossing. The operation of the highway crossing stick relays WSR and ESR an dof the highway crossing signals will be effected in the usual and wellknown manner. It will be understood, also, that Fig. 4 of the drawings showing the highway crossing modification of my invention may be inserted between any two sheets of the system shown in Fig. 1 ofthe drawings, such as between Figs. 1b and 1c, Figs-lc and 1d, or between any of these gures and' Fig. 3a or Fig. 3h when the stretch includes a track switch location. As will be apparent from the drawing of Fig; 4, the steady energy and track code of my system are carried around the approach sections at the highway crossing location over line wires which include front contacts of the track relays for these sections.

The operation is as follows, assuming that Fig. 4 is inserted between Figs. 1b and 1d. When steady energy is being received from location G of Fig. 1d and transmitted westbound, the code followingtrack relay ETR will be continuously energized, as will also the code transmitting relay WCI'M. The circuit for relay WCTM passesv over thev line wires and includes the` front points of contacts |58 and |59 of relay ECTM, front contacts |60 and I6| of track relay AETR, front contacts |62 and |63 of track relay OTR, back contacts |64 and |65 of the stick relays ERS and WSR, respectively, front contacts |66 and |61 of track relay AWTR, and the backpoints of contacts |68 and |69 of relay WTR. The energizationof relay WCTM applies steady energy to the track circuit WT west of the crossing location in the usual manner. When steady energy is removed at location G, as it will be when the westboundl entrance signal is cleared, relay WC'IM (and relay ETR) will become deenergized, thus permitting the code following track relay WTR to respond to code which is now being transmitted eastward from location D, since the trame direction is assumed to be westbound. The code operation of relay WTR will now cause relay ECTM to follow code and to repeat this code into the track section ET east of the crossing. 'I'he coding lcircuit for relay ECTM includes the front points of coding contacts |68 and |69 of relay WTRy the line circuit previously traced for relay WCTM, and the Iback points of contacts |58 and |59 of relay ETR. It will be apparent, therefore, that the presence of the highway crossing location within the single track stretch does not interfere in any manner with the transmission of either the steady energy or the coded energy which are used in establishing traffic in one or the other direction through the stretch. Also, there is no interference with the restoration ofthe system to its normal condition following the passage of a train over the stretch.

It will be noted that the line circuit in Fig. 4 is socontrolled by the eastbound and westbound track. relays that the two line wires transmit steady energy in one or the other direction according as the eastbound or the westbound track relay is steadily energized, and the same two line Wires` transmitcode in the other or the one direction according asfthe westbound or the eastbound track relay, respectively, is following code. The positive and negative source terminals (B and C, respectively)` at the two ends of the line circuit are connected in reverse order, so that when relay WTR is energized, the upper wire |93 has the positive energy terminal B connected thereto,v whereas when relay ETR is energized, this wire is connected with the negative energy .terminal C. The same is true for the lower wire |94 to which relay ETR connects positive energy and relay WTRV connects negative energy. Since theoperation ofthe system is such that relays 'WTR and E'I'R'areV never up at the same time, short` circuits other than Athose which might be caused by'ilashover at the contacts cannot develop, so thata single source could be used, if desired, for supplying energy at both ends of the line circuit. In order to decrease the possibility of excess current flowing should flashover occur at the contacts of' either relay ETR and WTR, I have provided a resistor |92 in the line circuit. This resistor is of insuflicient value to interfere with proper energization of relays ECTM and WCTM, but provides adequate protection against the possibility of an injurious short circuit.

It will be clear from the foregoing that by means of a novel and relatively simple line circuit control arrangement, I have made provision for safe and effective control of highway -oi relay ETFSA. When relay crossingA locations occurring within the single track stretch of my system; A

In all of the track circuits which I have shown, with the exception of the highway crossing track circuits and the detector track circuits at track switch locations, I employ track relays (TR.) having only a single contact finger which operates a repeater relay (TM) having the' required number of contacts. The reason why I prefer to use a single point track relay is'that this relay canbe designed to have greater shunting sensitivity, thus permitting the operation of much longer track circuits than wouldbepossible, for example, with a four point relay. It will be apparent, however, that where the track circuits need not be of extreme length, the repeater relayof the track relay may be dispensed with entirely, the track relay itself being equipped with the necessary number of contacts. f

Lighting of the various signals in my system may be vaccomplished in the usual manner which is Well known. It is intended, however, that the lever-controlled headblock signals at the ends of the sidings will be normally lighted, whereas the automatic intermediate signals will be normally dark but will become illuminated when an entrance signal is cleared or a train is approaching the intermediate signal location.

In describing the operation of the cut section apparatus at location F of Fig. 1c, a front contact coding cut section was used. By this is meant that repeating of the code around the cut section is accomplished over one or more front contacts. This type of cut section is satisfactory where the code received by a track relay is directly repeated into another track circuit and the total length of the track circuits which are so controlled, including the first one, is not excessive. However, the variation in track relay energization resulting from variation in track ballast resistance may be considerable in long track circuits, so that the time during which a front contact of a track relay is closed on code will appreciably increase when the relay is overenergized, resulting in distortion of the repeated code. This distortion may be cumulative'when the code is repeated over several cut sections ,by front contact coding, and may under certain conditions exceed the limits for proper operation of the decoding equipment. v

To avoid this difficulty, a back contact coding cut section such as I have shown in Fig. 5. may be used. This type of cut section has a corrective characteristic in that it repeats short on periods as long olf periods, and short off periods as long on periods'. ,Accordingly the distortion of code received by the rst track section will be compensated for, or largely corrected, by the use of the back contact coding cut section apparatus. The operation of this apparatus will be clear from the drawing so that only a brief explanation of the repeating circuits will be given. It will be noted that I have provided each track relay with an FSA lrelay which is energized when its track relay is operated either by steady energy or by code, and with a BSA relay which is operated only when the track relay is following code. In this manner, selective control is provided, depending upon whether steady energy or coded energy over the cut section. When relay ETR is steadily energized, for example, a steady energy circuit for relay WCTM is closed overthe back contact |95 of relay ETBSA and the front contact |96 is to be repeatedl ETR follows code, T5

ner previously the coderepeating circuit for relayv WCTM includesfthe' backpoint oi'v contact |91 of relay ETR, front contacts |98'and |99 of relays ETBSA and ETFSA, respectively, and back contact 200 of relay WTFSA. Corresponding circuits are'effective for operating relay ECTM on steady energy or code, according as relay WTR is steadily energized or is following track circuit code.

vReferring next to Fig. 1e which shows a modified form of the traffic direction control and traflic locking apparatusV of Fig. la., the apparatus of this figure is quite similar to that shown in Fig. la, the chief difference residing in the manner in which the polar stick relay BLPR is controlled, as well as the manner in which this relay controls the selective energization of the traffic direction control relays at the two ends of the stretch. With traflic assumed westbound and steady energy being received at the exit end (stretch unoccupied and both opposing headblock signals at stop), the westbound traffic relay EWFK will be energized so that its front contact 20| is closed. Since the traffic lever 8 occupies its normal position (traflic westbound), its contact 8W is closed so that polar relay BLPR is energized in the normal direction and contact ||0 occupies its right-hand position, as shown. Accordingly, the circuit for energizing terminal |02 is effective as soon as the starting button on lever 8 is depressed (so that relays 234ST and 234S are picked up). As pointed out hereinbefore, Venergization ofterminal |02 is effective in yenergizing the westbound trahie direction control relay BWFSR.

A reversal of lever 8, closing contact 8E, will be effective for reversing relay BLPR since the left-hand winding of this relay will! receive energy over front contact 20E of relay WFK and contact 8E of the lever. With relay BLPR reversed, an'energizing circuit for terminal |00 will be -effective whenever the starting button is depressed.vwhereupon the eastbound traic direction control relay 8EFSR'will be energized to effect the trail-lc direction reversal in the manexplained. The apparatus of Fig. le also employs a polar stick trafc indication relay BFK controlled to one or the other position over a front contact 202 or 203 of the associated relay SWFK cr SEFK. wPolar contact 204 of relay BFK controls the westbound and eastbound traiiic'indication.

One operating difference `between the apparatus 0f Fig. 1e andFig. la is that in the latter,

energizing circuitfor one or the other winding of relay SLPR is Vchecked over a Contact M08) of itsv corresponding indicating relay only, -but not over both indicating relays, as in Fig. 1e.

Accordingly, in Fig. la., a-reversal of relay 8LPR cannot be obtained yunless the steady energy is received at the end of the stretch corresponding Awith the established traic direction. Also, in Fig. la, the initial energizing circuit for terminal |02 or |04 includes a front Contact (|82 or IZi) --of the corresponding indication relay.- Thus,

neither traflic direction control relay can be energized from the ofce unless anindication is received, and this indication must correspond with A'the established traic direction. It will be clear, .'therefore, that the'apparatus of Fig. 1e will operate satisfactorily, but that additional renernents and checks have been introduced into the apparatus of Fig. 1a..

Fig. 1f shows a further modification of the apparatus of Fig. 1a. The apparatus of Fig. 1f -eliminatesthe polar stick relay BFK of Fig. le, 

